Rates from gradients and leaf discs, temperature and carbon dioxide data, and predicting rates and distances with the inverse square law (Higher).
What you will learn
- Calculate a rate of photosynthesis from a volume graph and a percentage change between rates
- Use rate = 1000 ÷ mean time, leaving out anomalies
- Read a temperature graph and explain the rise and fall
- Find where carbon dioxide stops limiting the rate and say what limits it next
- Predict a rate or find a distance with the inverse square law (Higher)
Rates from graphs and timings
On a graph of oxygen volume against time, the gradient is the rate: a steeper line means more oxygen each minute.
- Lamp at 10 cm: 24 cm³ in 10 minutes, rate = 24 ÷ 10 = 2.4 cm³/min
- Lamp at 30 cm: 8 cm³ in 10 minutes, rate = 8 ÷ 10 = 0.8 cm³/min
- (2.4 − 0.8) ÷ 0.8 × 100 = 200% increase
Another method times how long leaf discs take to float, as oxygen collects in them. A longer time means a slower rate, so a rate can be worked out as 1000 ÷ mean time. Leave out any anomalous result before you take the mean.
The rest of this lesson and its 11 practice questions are locked.
In this lesson
- Rates from graphs and timings
- Temperature and carbon dioxide
- The inverse square law in calculations (Higher)
- Try it: A rate from a graph
11 practice questions, marked as you go; about 30 minutes in all.
Key terms
Gradient, Optimum
In this unit: Bioenergetics: photosynthesis and respiration
Photosynthesis and its rate, limiting factors and the pondweed practical, aerobic and anaerobic respiration, exercise and metabolism.